perf: AABB snap pre-rejection via acadrust bounding_box() (Option K upgrade)

Add `aabb: [f32; 4]` field to WireModel (world-space 2-D bounding box).
In tessellate_entity() set each wire's AABB from e.as_entity().bounding_box()
via new entity_aabb() helper; Insert sub-entities each get their own AABB.
Preview/interim wires and any entity returning a zero-extent default box get
UNBOUNDED_AABB so they are never pre-rejected.

Replace the chord-sphere heuristic in Snapper::wire_in_range() with a proper
AABB vs snap-circle overlap test.  The new check is four scalar comparisons and
correctly handles closed curves (circles, arcs) which the chord-sphere approach
had to special-case.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/home/modify/stretch.rs

@@ -133,6 +133,7 @@ impl CadCommand for StretchCommand {
                     tangent_geoms: vec![],
                     aci: 0,
                     key_vertices: vec![],
+                    aabb: WireModel::UNBOUNDED_AABB,
                 })
             }
             _ => None,